CN117127098A - Preparation method of powder metallurgy high-speed steel wire - Google Patents

Abstract

The invention relates to the technical field of powder metallurgy, and discloses a preparation method of a powder metallurgy high-speed steel wire, which comprises the following components in percentage by weight: c: 1.5-1.8%, mn: 0.28-0.38%, si: 0.6-0.75%, cr: 3.8-4.5%, V or Nb+V: 2.8-3.2%, W: 5.8-6.5%, mo: 4.8-5.5%, co: 7.8-8.5%, ti: 1.8-2.3%, re: 1-3%, S: <0.03%, P: <0.05%, o+n+h: <0.005%, the balance being Fe. The powder metallurgy high-speed steel prepared by the method has the advantages of fine structure, uniform carbide, less harmful impurity quantity, and obviously improved bending strength, toughness and wear resistance.

Description

A kind of preparation method of powder metallurgy high-speed steel wire

Division description

This invention is a divisional application with an application date of June 2, 2022, an application number of 2022106182756, and an invention title of “Powder Metallurgy High Speed Steel Wire Material and Preparation Method thereof”.

Technical field

The invention relates to the technical field of powder metallurgy, and in particular to a method for preparing powder metallurgy high-speed steel wire.

Background technique

High-speed steel has the characteristics of high hardness, high strength, and good wear resistance, and is widely used in precision tool manufacturing and mold manufacturing. Compared with traditional cast high-speed steel, high-speed steel prepared by powder metallurgy significantly improves the problem of carbide segregation in the microstructure, greatly improving the material's mechanical properties and working stability. Currently, commercially available powder metallurgy high-speed steel is mainly prepared by a combination of gas atomized alloy powder and hot isostatic pressing. The obtained high-speed steel has an obvious fine-grained structure, uniform distribution of carbides, and strength properties above 3500MPa. Some grades have It can reach more than 4000MPa, but due to the high cost of production, its large-scale application is seriously limited. There are research reports that using commercial M2 alloy powder doped with vanadium nitride powder through ball milling activation and cold pressing sintering, the material can be basically densified at 1160°C, with a relative density as high as 99.4%, and the strength performance can be maintained at 2500~ About 3000MPa, and greatly reduces production costs. Therefore, the present invention aims to disclose a method for preparing low-cost, high-performance powder metallurgy high-speed steel by cold pressing sintering.

Contents of the invention

Purpose of the invention: Aiming at the problem of low service life of high-speed steel materials, the present invention provides a method for preparing powder metallurgy high-speed steel wire. The prepared powder metallurgy high-speed steel has a fine structure, uniform carbides, low amounts of harmful impurities, and high flexural strength, toughness and Wear resistance is significantly improved.

Technical solution: The present invention provides a powder metallurgy high-speed steel wire, including the following components by weight: C: 1.5~1.8%, Mn: 0.28~0.38%, Si: 0.6~0.75%, Cr: 3.8~4.5% , V or Nb+V: 2.8~3.2%, W: 5.8~6.5%, Mo: 4.8~5.5%, Co: 7.8~8.5%, Ti: 1.8~2.3%, Re: 1~3%, S: < 0.03%, P: <0.05%, O+N+H: <0.005%, and the rest is Fe.

The invention also provides a method for preparing powder metallurgy high-speed steel wire, which includes the following steps: S1: Melting the master alloy: taking the pure metal of the raw material Fe according to the proportion, and the pure metal of W, Mo, Co, V, Nb, and Cr respectively. Metal or master alloy, as well as master alloys of C-Fe, Si-Fe, Mn-Fe, Ti-C, Re-M, and dry all raw materials; under the condition of vacuum degree 10 ^-5 ~ 10 ³ Pa Melt the master alloy; first melt the pure metals among Fe, W, Mo, Co, V, Nb, and Cr at 1380 to 1580°C, and keep it warm for 10 to 15 minutes; then add W, Mo, Co, V, and Nb at 1280 to 1580°C. , Cr master alloy and C-Fe, Si-Fe, Mn-Fe master alloy, keep the temperature for 10 to 15 minutes, stir evenly and then remove the slag; again add the bulk material made of Ti-C powder at 1280 to 1580°C , keep the temperature for 15~35min; then add the Re-M master alloy at 1280~1480℃, keep it for 3~5min, and keep electromagnetic stirring during the insulation process; finally, cast it in the vacuum furnace to get the master alloy; S2: electroslag purification: for S1 The prepared master alloy is subjected to electroslag remelting. The electroslag slag system is CaF ₂ -CaO-Al ₂ O ₃ -TiO ₂ , with contents of 65 to 70%, 10 to 15%, 10 to 15, and 5 to 10% respectively. ; S3: Pulverizing: Powder the master alloy purified by S2 electroslag to obtain alloy powder; S4: Annealing and compacting: The alloy powder is sequentially subjected to reduction annealing and powder compacting to prepare a powder block blank; S5: Sintering: sintering the powder block blank obtained in S4; S6: heat treatment: performing graded heat treatment on the sintered powder block blank obtained in S5; S7: deformation: forging and/or extruding the powder block blank obtained in S6 , rolling, and drawing treatments to obtain wires with φ1-3mm; S8: heat treatment: perform graded heat treatment on the wires obtained in S7 again.

Preferably, in S2, during the electroslag remelting process, the temperature gradient of the molten pool is controlled by means of enhanced cooling at the outlet of the crystallizer and appropriate insulation of the side walls, so that the solidification direction is consistent with the side walls of the molten pool. The acute angle part of the angle between the walls ranges from 0 to 30°, and the purified master alloy melt is obtained.

Preferably, in S3, the master alloy purified by S2 electroslag is transferred to an intermediate furnace protected by a protective atmosphere and the inner wall of the furnace is plated with a protective layer, and then directly pulverized in the intermediate furnace to obtain the alloy powder.

Further, in the S3, the powdering method is gas atomization powdering, using argon gas atomization, argon gas purity 99.9%, atomization pressure 10-30MPa, and the D50 of the prepared alloy powder is 20 ~60 μm; or, the powdering method is water and gas combined atomization powdering, the gas used is argon, the purity is 99.9%, the atomization pressure is 10-30MPa, the water pressure is 8-50MPa, and the prepared alloy The D50 of the powder is 8 to 20 μm; or the powder making method is ball milling, and the D50 of the prepared alloy powder is 8 to 50 μm; or the powder making method is rotary ionization powdering, and the prepared alloy powder The D50 of the alloy powder is 30 to 70 μm.

Preferably, in S4, the reduction annealing process is as follows: carried out in a vacuum furnace, the furnace is in a vacuum state or an inert gas protection state, and the powder is laid flat on the substrate with a thickness of 5 to 10 mm, and the multi-layer The substrates are placed on top of each other, with a distance of 30 to 100 mm between adjacent substrates, a temperature of 400 to 680°C, a holding time of 60 to 300 minutes, and then taken out after cooling to room temperature in the furnace. During the process, the oxygen content of the atmosphere in the furnace is detected to ensure that the oxygen content is less than 10 ppm.

Further, in S4, the powder compacting process is non-HIP compacting: weigh the alloy powder after reduction annealing and put it into a compacting mold, and bidirectionally mold the powder into a block blank; Pressure 500~1200MPa.

Further, in S5, the sintering method is atmospheric pressure protective atmosphere sintering: (1) Inject protective inert gas into the sintering furnace and discharge oxygen to make the oxygen content in the sintering furnace less than 1 ppm; (2) ) Heating to 650~850℃ at a speed of 6~10℃/min, holding time t=3~5min/cm×d; (3) Heating to 1180~1260℃ at a speed of 8~10℃/min, keeping warm Time t=10~30min/cm×d; (4) Cool to room temperature with the furnace; where d is the maximum wall thickness of the sample, in cm.

Preferably, in the S6 and/or S8, the stepwise heat treatment process is as follows: (1) Preheating: heating to 580~620°C at a temperature rise rate of 5~10°C/min, with a holding time of t=3~ 5min/cm×d; (2) Secondary preheating: then heat to 840～860℃ at a heating rate of 5～10℃/min, holding time t=2～4min/cm×d; (3) Quenching and heat preservation : Then heat to 1170~1260°C at a heating rate of 5~10℃/min, holding time t=2~4min/cm×d; (4) Quenching and cooling: Then, when d≥10, first with 10 Cool down to 300~500℃ at a cooling rate of ³ ~10 ⁵ ℃/s, keep warm for t=0.1~1.5min/cm×d, and then cool down to 20~40℃ at a cooling speed of 10 ³ ~10 ⁵ ℃/s. Heating time t=0.1~1.5min/cm×d; when 10≥d≥5, cool down to 200~400℃ at a cooling rate of 10 ³ ~ 10 ⁵ ℃/s, holding time t=0.1~1.5min/cm ×d, then cool to 20~40℃ at a cooling rate of 10 ³ ~ 10 ⁵ ℃/s, ^holding time t = 0.1 ~ ^1.5 min/cm Cool down to 20~40℃ at a cooling speed of s, and keep the temperature t=0.1~1.5min/cm×d; (5) Cryogenic treatment: Then cool down to -50~- at a cooling speed of 10 ⁵ ~ 10 ⁷ ℃/s. 150℃, holding time t=1～2min/cm×d; (6) Tempering: then heat to 560～570℃ at a heating rate of 5～10℃/min, holding time t=1～3h/cm× d; (7) Cooling: followed by rapid cooling to 200~300℃, holding time t=0.3~1h/cm×d, air cooling to 20~40℃ after leaving the oven; (8) Repeat (6) and (7) 0~ 1 time; where, d is the maximum wall thickness of the sample, in cm. Due to its particularity, the heat treatment process of powdered high-speed steel is also different from that of ordinary metals. The main difference is that it requires preheating, higher quenching temperature, high tempering temperature and many times of tempering; the internal stress of the powdered high-speed steel bar after deformation is relatively high. Large and very hard, it must be annealed first. The annealing temperature is 840~880℃, and the annealing time t=2~20min/cm×d. High-speed steel contains more alloy elements and has poor thermal conductivity. It must be preheated before heating. The preheating temperatures are 580~620℃ and 840~880℃, and the preheating time t=2~5min/cm×d. The quenching temperature is 1170~1260℃. After quenching, it is water-cooled or oil-cooled to room temperature. Finally, temper three times at 560~570℃, each holding time t=1~3h×d. The following four points must be paid attention to when tempering high-speed steel: (1) Tempering must be carried out in time after quenching, otherwise the austenite will be stabilized, which is not conducive to the elimination of residual austenite (generally no more than 8 hours), (2) The tempering temperature should be as high as possible Uniformly, it is best to conduct it in a salt bath furnace or a well-type tempering furnace with a fan, and strive to heat evenly. (3) After each tempering, it must be cooled to room temperature before subsequent temperings can be repeated. (4) After tempering, it must be cooled Do not wash until it reaches room temperature, otherwise it will easily deform and crack. The grains and second phase of the powdered high-speed steel prepared under these conditions are evenly refined, and fine and dispersed granular carbides are distributed on the tempered martensite base. Unclosed pores are round or oval in shape. The hardness reaches 67.5HRC, the red hardness reaches 63.2HRC, and the bending strength reaches 4146.3MPa. Preferably, in S6, the pre-deformation annealing process is as follows: heat the powder block blank to 850-870°C in a vacuum furnace or salt bath furnace at a heating rate of ≤2.5°C/min, and keep it warm for 110 After ~130min, raise the temperature to 1100~1300℃ at a heating rate of ≤400℃/h, keep it for 15~30min, then lower the temperature to 850~870℃, keep it for 60~120min, and then heat it in the furnace at a temperature of 10~30℃/h. The cooling rate is lowered to 500~600℃, and then air-cooled or cooled to about 200℃ with the furnace, and then air-cooled to room temperature after being discharged from the furnace.

The invention also provides a method for preparing powder metallurgy high-speed steel wire, which includes the following steps: S1: Take pure metal of raw material Fe, pure metal or intermediate alloy of W, Mo, Co, V, Nb, and Cr according to the proportion. , as well as master alloys of C-Fe, Si-Fe, Mn-Fe, Ti-C, Re-M, and dry all raw materials; use vacuum induction under the condition of vacuum degree 10 ^-5 ~ 10 ³ Pa Melting technology melts the master alloy; first, melt the pure metals among Fe, W, Mo, Co, V, Nb, and Cr at 1380 to 1580°C, and keep it warm for 10 to 15 minutes; secondly, add W, Mo, Co, and V at 1280 to 1580°C. , Nb, Cr master alloy and C-Fe, Si-Fe, Mn-Fe master alloy, keep the temperature for 10 to 15 minutes, stir evenly and then remove the slag; again add the block made of Ti-C powder at 1280 to 1580°C The body material is kept at a temperature of 15 to 35 minutes; then the Re-M master alloy is added at 1280 to 1480°C and kept at a temperature of 3 to 5 minutes, with electromagnetic stirring during the insulation process; finally, it is cast in a vacuum furnace to obtain the master alloy; S2: Prepared for S1 The master alloy is electroslag remelted; S3: The S2 electroslag remelted master alloy is drop-cast into a copper mold in a protective atmosphere to obtain a drop-cast ingot; S4: The S3 ingot is crushed and ball milled Powder making; S5: Sequentially perform reduction annealing and powder compaction on the S4 alloy powder to prepare a powder block blank; S6: Sinter the powder block blank obtained in S5; S7: Sinter the powder block blank obtained in S6. Classification heat treatment; S8: Forging and/or extrusion, rolling, and drawing of the powder block blank obtained in S7 to obtain a wire material of φ1-3mm; S9: Performing classification heat treatment on the wire material obtained in S8 again.

Preferably, in S4, the ball milling process is as follows: S4-1: crush the drop-cast ingot obtained in S3 to 0.1-1 mm; S4-2: mix the powder into alcohol with a planetary ball mill, and mix the balls with The weight ratio of the powder is 3 to 6:1, and the grinding time is 24 to 72 hours; S4-3: Dry the ground mixed slurry at 75 to 80°C for 5 to 10 hours, sieve and then transfer to low oxygen content. Perform certain pre-oxidation in a pressurized drying chamber; S4-4: Seal and store the powder obtained in S3.

Preferably, one of TiC, VN, WC, Mo ₂ C, Cr ₃ C ₂ , VC, NbC powder or a combination thereof is added during the ball milling process. Because elements will be burned during the smelting process, there will be a slight deviation in the composition after the powder is made. By adding carbide or nitride raw powder of the corresponding alloy elements, the composition can be accurately adjusted to the upper or lower limit to better determine the microscopic organization, and ultimately performance.

Further, in step S6, the sintering method is HIP sintering: (1) Put the powder block blank into the hollow shell, vacuum it, and seal it; (2) At a speed of 8-12°C/min Raise the temperature to 600~700℃, holding time t=2~8min/cm×d; (3) heat up to 1100~1250℃ at a speed of 5~15℃/min, holding time t=15~25min/cm×d; (4) Cool to room temperature in the furnace; where d is the maximum wall thickness of the sample, in cm.

Beneficial effects: (1) In the present invention, during electroslag remelting, the slag system of electroslag is CaF ₂ -CaO-Al ₂ O ₃ -TiO ₂ , which can remove the inner wall of the furnace and the surface of the casting mold of the master alloy during the smelting stage. The fallen non-metallic inclusions can improve the purity of the master alloy, reduce the stress concentration problem caused by non-metallic inclusions, and improve the toughness and fatigue resistance of the material; and since TiO ₂ is added to the slag system, according to the principle of chemical kinetic equilibrium, it can It prevents the diffusion of Ti in the master alloy to the slag layer, increases the yield of Ti in the master alloy, refines the grains, and improves performance.

(2) In the present invention, the master alloy purified by electroslag is directly transferred to the intermediate furnace, and then atomized and pulverized. The advantage is that the master alloy purified by electroslag has higher purity and will not cause secondary damage due to re-melting. Contamination, the powder obtained in this way is of higher purity, with 90% less non-metallic inclusions and harmful gas content compared to ordinary methods.

(3) In the present invention, the Re rare earth element is added to the component, mainly to remove the impurity element oxygen in the component. Because the chemical properties of Re element are very active, it can reduce almost all metal oxides and generate stable Re-O oxides. It can not only purify components and reduce the harm of harmful element O, but also form Re-O oxides. It can be used as the core of heterogeneous nucleation, increase the heterogeneous nucleation rate, refine the grains, and improve the strength and toughness. In addition, the Re-M master alloy is added in the vacuum melting and electroslag refining stages respectively, in order to improve the utilization rate of Re-M and prevent the burning loss from being too severe when all the Re-M is added in the vacuum melting stage, which cannot ensure sufficient removal of the molten metal in the melt. oxygen, ultimately making the melt purer.

(4) TiC, VN, WC, Mo ₂ C, Cr ₃ C ₂ , VC, NbC and other alloy powders are added during the preparation process to provide a large number of non-uniform nucleation cores for solidification and recrystallization, and promote heterogeneous nucleation. It plays the role of refining the grain size and carbide size, and is beneficial to improving the material's mechanical properties such as hardness, wear resistance and flexural strength.

(5) In the present invention, the master alloy after electroslag remelting is drop-casted into a copper mold in a protective atmosphere to obtain a drop-cast ingot. The benefits are: the size of the droplets is small and the solidification speed is fast. Effectively suppresses the segregation of alloy elements and makes the alloy composition more uniform, which is very important to ensure the performance of high-speed steel; drop-casting into the copper mold, the copper mold can quickly dissipate heat, further accelerate the solidification speed, and ensure the uniformity of the composition ; Perform drop casting in a protective atmosphere to prevent oxygen in the air from contaminating the solution and reducing the harm of oxygen; the drop cast ingot has many weld marks to facilitate the next step of crushing.

(6) In the present invention, graded quenching is performed according to the wall thickness of the material, and different isothermal temperatures are selected according to different wall thicknesses, so that the temperature of the material and the heat on the surface and inside of the material can be evenly and quickly dissipated, which not only eliminates Stress cracking caused by uneven heat distribution can also better achieve the purpose of quenching the material (transforming austenite to martensite or lower bainite). In addition, the cryogenic treatment after quenching can further promote the transformation of retained austenite into martensite and improve the hardness and toughness of the material.

Description of the drawings

Figure 1 is the process diagram of graded heat treatment (d≥10 or 10≥d≥5);

Figure 2 is a process diagram of graded heat treatment (d≤5cm).

Detailed ways

The present invention will be introduced in detail below with reference to the accompanying drawings.

The invention provides a powder metallurgy high-speed steel wire, which contains the following components by weight: C: 1.5-1.8%, Mn: 0.28-0.38%, Si: 0.6-0.75%, Cr: 3.8-4.5%, V or Nb+V: 2.8～3.2%, W: 5.8～6.5%, Mo: 4.8～5.5%, Co: 7.8～8.5%, Ti: 1.8～2.3%, Re: 1～3%, S: <0.03%, P: <0.05%, O+N+H: <0.005%, and the rest is Fe.

The preparation method of the above-mentioned powder metallurgy high-speed steel wire is as follows:

Example 1:

This embodiment provides a method for preparing powder metallurgy high-speed steel wire, including the following steps: S1: Melting the master alloy: taking the pure metal of the raw material Fe according to the proportion, and the pure metal of W, Mo, Co, V, Nb, and Cr respectively. Metal or master alloy, as well as master alloys of C-Fe, Si-Fe, Mn-Fe, Ti-C, Re-M, and dry all raw materials; under the condition of vacuum degree 10 ^-5 ~ 10 ³ Pa Melt the master alloy; first melt the pure metals among Fe, W, Mo, Co, V, Nb, and Cr at 1380 to 1580°C, and keep it warm for 12 minutes; then add W, Mo, Co, V, Nb, and Cr at 1280 to 1580°C. The master alloy and the master alloy of C-Fe, Si-Fe, Mn-Fe, keep the temperature for 12 minutes, stir evenly and then remove the slag; add the bulk material pressed by Ti-C powder again at 1280~1580°C, and keep the temperature for 30 minutes; Then add the Re-M master alloy at 1280~1480℃, keep it for 4 minutes, and keep electromagnetic stirring during the holding process; finally, it is cast in a vacuum furnace and the master alloy is obtained;

S2: Electroslag purification: The master alloy prepared in S1 is electroslag remelted. The electroslag slag system is CaF ₂ -CaO-Al ₂ O ₃ -TiO ₂ , with contents of 70%, 12%, 12%, and 8 respectively. %, the master alloy after electroslag purification is obtained;

At the same time as the above-mentioned electroslag remelting, the cooling capacity of the crystallizer outlet is enhanced (using cooling water or directly pulling one end of the billet into the water) and the method of insulating the side walls of the molten pool (coil heating + sensor) to control the melt pool. The temperature gradient keeps the angle between the solidification direction and the side wall of the molten pool at 20 to 30°, and the purified master alloy melt is obtained.

S3: Pulverizing: Pulverize the master alloy purified by S2 electroslag to obtain alloy powder;

The above-mentioned powder making method is gas atomization powder making, using argon gas atomization, the argon gas purity is 99.9%, the atomization pressure is 10 MPa, and the D50 of the prepared alloy powder is 20 μm.

S4: Annealing and compacting: perform reduction annealing and powder compacting on the alloy powder in sequence to prepare a powder block blank;

The above-mentioned reduction annealing process is as follows:

It is carried out in a vacuum furnace. The furnace is in a vacuum state or an inert gas protection state. The powder is laid flat on the substrate with a thickness of 5mm. Multiple layers of substrates are placed on top of each other. The distance between adjacent substrates is 30mm. The temperature is 400°C. The holding time is 60min. After the furnace cools to room temperature, take it out. During the process, the oxygen content of the atmosphere in the furnace is detected to ensure that the oxygen content is less than 10 ppm.

The above-mentioned powder compacting process is non-HIP compacting: weigh the alloy powder after reduction annealing and put it into a compacting mold, and press the powder in two directions to form a block blank; the pressure is 1200MPa.

S5: Sintering: Sintering the powder block blank obtained in S4;

The above-mentioned sintering method can be atmospheric pressure protective atmosphere sintering: (1) Pour protective inert gas into the sintering furnace and discharge oxygen to make the oxygen content in the sintering furnace less than 1ppm; (2) Raise the temperature at a rate of 10°C/min to 650°C, holding time t=5min/cm×d; (3) heating to 1220°C at a rate of 10°C/min, holding time t=20min/cm×d; (4) cooling to room temperature with the furnace; where , d is the maximum wall thickness of the sample, in cm.

S6: Heat treatment: perform graded heat treatment on the sintered powder block blank obtained in S5;

The process of the above-mentioned graded heat treatment is as follows (Figures 1 and 2):

(1) Preheating: Heating to 580°C at a heating rate of 5°C/min, holding time t=3min/cm×d;

(2) Secondary preheating: then heat to 840°C at a heating rate of 5°C/min, holding time t=2min/cm×d;

(3) Quenching and heat preservation: then heated to 1170°C at a temperature rise rate of 5°C/min, holding time t=2min/cm×d;

(4) Quenching and cooling: Immediately afterwards,

When d≥10, first cool down to 300°C at a cooling rate of 10 ⁴ ℃/s, holding time t = 1 min/cm × d, and then cool down to 20°C at a cooling rate of 10 ⁴ ℃/s, holding time t = 1.5min/cm×d (as shown in Figure 1);

When 10≥d≥5, cool down to 200℃ at a cooling rate of 10 ⁵ ℃/s, holding time t=1min/cm×d, then cool down to 40℃ at a cooling rate of 10 ⁴ ℃/s, holding time t =1.5min/cm×d (as shown in Figure 1);

When d≤5cm, cool to 40°C at a cooling rate of 10 ⁵ °C/s, and the holding time is t=1.5min/cm×d (as shown in Figure 2);

(5) Cryogenic treatment: then cool to -100°C at a cooling rate of 10 ⁵ °C/s, holding time t=1min/cm×d;

(6) Tempering: then heat to 560°C at a heating rate of 5°C/min, holding time t=1h/cm×d;

(7) Cooling: followed by cooling to 200°C in the furnace, and air cooling to 40°C after exiting the furnace;

(8) Repeat (6) and (7) at least once;

Among them, d is the maximum wall thickness of the sample, in cm.

S7: Deformation: The powder block blank obtained in S6 is forged and/or extruded, rolled, and drawn to obtain a φ2mm wire;

The above-mentioned forging process is as follows:

Preheating: First, heat the blank to 620°C at a heating rate of 8°C/min, holding time t=3min/cm×d; then heat to 860°C at a heating rate of 8°C/min, holding time t=2min/cm ×d; where, d is the maximum wall thickness of the sample, in cm;

Forging: Forge the billet, reducing the amount by 5% each time. After each forging, directly put the billet back into the furnace at 840°C for heating. The heating time is t=3min/cm×d until the billet is forged to the desired temperature. Size required;

Cooling: Place the forged billet into the furnace and cool it to 200°C, then take it out of the furnace and air-cool it to room temperature.

The above-mentioned extrusion method is hot extrusion, and the process is as follows:

Preheating: First, heat the blank to 620°C at a heating rate of 7°C/min, holding time t=5min/cm×d; then heat to 900°C at a heating rate of 7°C/min, holding time t=4min/cm ×d; where, d is the maximum wall thickness of the sample, in cm;

Hot extrusion: The extrusion method is horizontal extrusion, the extrusion speed is 5mm/s, the single extrusion cross-section is reduced by 8%, and the extrusion die preheating temperature is 750°C;

Cooling: Put the extruded billet into the furnace and cool it to 260°C, then take it out of the furnace and air-cool it to room temperature.

S8: Heat treatment: The wire obtained in S7 is subjected to graded heat treatment again. The hierarchical heat treatment process in this step is shown in Figures 1 and 2. It is the same as the process in S6 above and will not be described again here.

Example 2:

This embodiment is roughly the same as Embodiment 1. The only difference is that in this embodiment, in step S3, the master alloy purified by S2 electroslag is pulverized by combined water and gas atomization pulverization. It is argon gas with a purity of 99.9%, an atomization pressure of 10MPa, and a water pressure of 20MPa. The D50 of the prepared alloy powder is 10 μm.

Except for this, this embodiment is exactly the same as Embodiment 1, and will not be described again here.

Example 3:

This embodiment is roughly the same as Embodiment 1. The only difference is that in this embodiment, in step S3, the master alloy purified by S2 electroslag is pulverized by ball milling. The prepared alloy powder is D50 is 50μm.

Except for this, this embodiment is exactly the same as Embodiment 1, and will not be described again here.

Example 4:

This embodiment provides a method for preparing powder metallurgy high-speed steel wire, including the following steps: S1: Melting the master alloy: taking the pure metal of the raw material Fe according to the proportion, and the pure metal of W, Mo, Co, V, Nb, and Cr respectively. Metal or master alloy, as well as master alloys of C-Fe, Si-Fe, Mn-Fe, Ti-C, Re-M, and dry all raw materials; under the condition of vacuum degree 10 ^-5 ~ 10 ³ Pa Melt the master alloy; first melt the pure metals among Fe, W, Mo, Co, V, Nb, and Cr at 1380 to 1580°C, and keep it warm for 12 minutes; then add W, Mo, Co, V, Nb, and Cr at 1280 to 1580°C. The master alloy and the master alloy of C-Fe, Si-Fe, Mn-Fe, keep the temperature for 12 minutes, stir evenly and then remove the slag; add the bulk material pressed by Ti-C powder again at 1280~1580°C, and keep the temperature for 30 minutes; Then add the Re-M master alloy at 1280~1480℃, keep it for 4 minutes, and keep electromagnetic stirring during the holding process; finally, it is cast in a vacuum furnace and the master alloy is obtained;

S2: Electroslag remelting of the master alloy prepared in S1;

At the same time as the above-mentioned electroslag remelting, the cooling capacity of the crystallizer outlet is enhanced (using cooling water or directly pulling one end of the billet into the water) and the method of insulating the side walls of the molten pool (coil heating + sensor) to control the melt pool. The temperature gradient keeps the angle between the solidification direction and the side wall of the molten pool at 20 to 30°, and the purified master alloy melt is obtained.

S3: Drop-cast the master alloy remelted by S2 electroslag into a copper mold in a protective atmosphere to obtain a drop-cast ingot;

S4: Crush the ingot of S3 and grind it into powder;

The above-mentioned ball milling process is as follows:

S4-1: Crush the drop-cast ingot obtained in S3 to 0.1~1mm;

S4-2: Use a planetary ball mill to mix the powder into alcohol. The weight ratio of balls to powder is 5:1, and the grinding time is 50 hours;

S4-3: Dry the ground mixed slurry at 78°C for 8 hours, screen it and transfer it to a drying chamber with low oxygen partial pressure for certain pre-oxidation;

S4-4: Seal and store the alloy powder obtained in S4-3.

During the above-mentioned ball milling process, by detecting the average composition of the powder, if the content of alloy elements does not meet the requirements, TiC, VN, WC, Mo ₂ C, Cr ₃ C ₂ , VC, and NbC powders are added accordingly. One or a combination thereof, so that the final alloy powder meets the composition requirements.

S5: The S4 alloy powder is sequentially subjected to reduction annealing and powder compacting to prepare a powder block blank;

The above-mentioned reduction annealing process is as follows:

It is carried out in a vacuum furnace. The furnace is in a vacuum state or an inert gas protection state. The powder is laid flat on the substrate with a thickness of 5mm. Multiple layers of substrates are placed on top of each other. The distance between adjacent substrates is 30mm. The temperature is 400°C. The holding time is 60min. After the furnace cools to room temperature, take it out. During the process, the oxygen content of the atmosphere in the furnace is detected to ensure that the oxygen content is less than 10 ppm.

The above-mentioned powder compacting process is non-HIP compacting: weigh the alloy powder after reduction annealing and put it into a compacting mold, and press the powder in two directions to form a block blank; the pressure is 1200MPa.

S6: Sintering the powder block blank obtained in S5;

The above-mentioned sintering method can be atmospheric pressure protective atmosphere sintering: (1) Pour protective inert gas into the sintering furnace and discharge oxygen to make the oxygen content in the sintering furnace less than 1ppm; (2) Raise the temperature at a rate of 10°C/min to 650℃, holding time t=5min/cm×d; (3) heating to 1220℃ at a speed of 10℃/min, holding time t=20min/cm×d; (4) cooling to room temperature with the furnace; where, d is the maximum wall thickness of the sample, in cm.

S7: Perform graded heat treatment on the sintered powder block blank obtained in S6;

The process of the above-mentioned graded heat treatment is as follows (Figures 1 and 2):

(1) Preheating: Heating to 580°C at a heating rate of 5°C/min, holding time t=3min/cm×d;

(2) Secondary preheating: then heat to 840°C at a heating rate of 5°C/min, holding time t=2min/cm×d;

(3) Quenching and heat preservation: then heated to 1170°C at a temperature rise rate of 5°C/min, holding time t=2min/cm×d;

(4) Quenching and cooling: Immediately afterwards,

When d≥10, first cool down to 300°C at a cooling rate of 10 ⁴ ℃/s, holding time t = 1 min/cm × d, and then cool down to 20°C at a cooling rate of 10 ⁴ ℃/s, holding time t = 1.5min/cm×d (as shown in Figure 1);

When 10≥d≥5, cool down to 200℃ at a cooling rate of 10 ⁵ ℃/s, holding time t=1min/cm×d, then cool down to 40℃ at a cooling rate of 10 ⁴ ℃/s, holding time t =1.5min/cm×d (as shown in Figure 1);

When d≤5cm, cool to 40°C at a cooling rate of 10 ⁵ °C/s, and the holding time is t=1.5min/cm×d (as shown in Figure 2);

(5) Cryogenic treatment: then cool to -100°C at a cooling rate of 10 ⁵ °C/s, holding time t=1min/cm×d;

(6) Tempering: then heat to 560°C at a heating rate of 5°C/min, holding time t=1h/cm×d;

(7) Cooling: followed by cooling to 200°C in the furnace, and air cooling to 40°C after exiting the furnace;

(8) Repeat (6) and (7) at least once;

Among them, d is the maximum wall thickness of the sample, in cm.

S8: Perform forging, extrusion, rolling, and drawing on the powder block blank obtained in S7 to obtain a φ2mm wire material;

The above-mentioned forging process is as follows:

Preheating: First, heat the blank to 620°C at a heating rate of 8°C/min, holding time t=3min/cm×d; then heat to 860°C at a heating rate of 8°C/min, holding time t=2min/cm ×d; where, d is the maximum wall thickness of the sample, in cm;

Forging: Forge the billet, reducing the amount by 5% each time. After each forging, directly put the billet back into the furnace at 840°C for heating. The heating time is t=3min/cm×d until the billet is forged to the desired temperature. Size required;

Cooling: Place the forged billet into the furnace and cool it to 200°C, then take it out of the furnace and air-cool it to room temperature.

The above-mentioned extrusion method is hot extrusion, and the process is as follows:

Preheating: First, heat the blank to 620°C at a heating rate of 7°C/min, holding time t=5min/cm×d; then heat to 900°C at a heating rate of 7°C/min, holding time t=4min/cm ×d; where, d is the maximum wall thickness of the sample, in cm;

Hot extrusion: The extrusion method is horizontal extrusion, the extrusion speed is 5mm/s, the single extrusion cross-section is reduced by 8%, and the extrusion die preheating temperature is 750°C;

Cooling: Put the extruded billet into the furnace and cool it to 260°C, then take it out of the furnace and air-cool it to room temperature.

S9: The wire material obtained in S8 is subjected to graded heat treatment again. The hierarchical heat treatment process in this step is shown in Figures 1 and 2. It is the same as the process in S6 above and will not be described again here.

Example 5:

This embodiment is substantially the same as Embodiment 4, and the only difference lies in that, in this embodiment,

S5: S4 alloy powder is subjected to reduction annealing and powder compaction in sequence to prepare a powder block blank; the above powder compaction process is HIP compaction: weigh the alloy powder after reduction annealing and put it into the compaction mold , carry out HIP compaction, and press the powder into a block blank at a pressure of 120 to 500MPa.

S6: Sintering the powder block blank obtained in S5;

The above-mentioned sintering method is HIP sintering: (1) Put the powder block blank into the hollow shell, evacuate and seal; (2) Raise the temperature to 650°C at a speed of 10°C/min, and keep the temperature t=5min/ cm×d; (3) Heating to 1180°C at a rate of 10°C/min, holding time t=20min/cm×d; (4) Cooling to room temperature in the furnace; where d is the maximum wall thickness of the sample, in cm .

Except for this, this embodiment is exactly the same as Embodiment 4, and will not be described again here.

Example 6:

This embodiment is substantially the same as Embodiment 4, and the only difference lies in that, in this embodiment,

S8: Forge, roll, and draw the powder block blank obtained in S7 to obtain a φ2mm wire;

The above-mentioned forging process is as follows:

Preheating: First, heat the blank to 620°C at a heating rate of 8°C/min, holding time t=3min/cm×d; then heat to 860°C at a heating rate of 8°C/min, holding time t=2min/cm ×d; where, d is the maximum wall thickness of the sample, in cm;

Forging: Forge the billet, reducing the amount by 5% each time. After each forging, directly put the billet back into the furnace at 840°C for heating. The heating time is t=3min/cm×d until the billet is forged to the desired temperature. Size required;

Cooling: Place the forged billet into the furnace and cool it to 200°C, then take it out of the furnace and air-cool it to room temperature.

Except for this, this embodiment is exactly the same as Embodiment 4, and will not be described again here.

Comparative example 1:

The wire material was prepared using the formula and method disclosed in the paper "Peng Hanlin, Research on the heat treatment rules of powder metallurgy high-speed steel S390/S790 for fine blanking dies, Huazhong University of Science and Technology, 2020."

Table 1 below shows the properties of the wires prepared using the formulations of Examples a to c using Examples 1 to 6 respectively and the properties of the wire prepared in Comparative Example 1.

Table 1

The above embodiments are only for illustrating the technical concepts and features of the present invention. Their purpose is to enable those familiar with this technology to understand the content of the present invention and implement it accordingly, and cannot limit the scope of protection of the present invention. All equivalent transformations or modifications made based on the spirit and essence of the present invention shall be included in the protection scope of the present invention.

Claims (8)

1. A method for preparing powder metallurgy high-speed steel wire, characterized in that the powder metallurgy high-speed steel wire contains the following components by weight: C: 1.5~1.8%, Mn: 0.28~0.38%, Si: 0.6~0.75 %, Cr: 3.8~4.5%, V or Nb+V: 2.8~3.2%, W: 5.8~6.5%, Mo: 4.8~5.5%, Co: 7.8~8.5%, Ti: 1.8~2.3%, RE: 1~3%, S: <0.03%, P: <0.05%, O+N+H: <0.005%, the rest is Fe; its preparation method includes the following steps: S1: According to the proportion, pure metal of raw material Fe, pure metal or master alloy of W, Mo, Co, V, Nb, Cr, and C-Fe, Si-Fe, Mn-Fe, Ti-C, RE- M master alloy, and dry all raw materials; use vacuum induction melting technology to melt the master alloy under the condition of vacuum degree of 10 ^-5 ~ 10 ³ Pa; first melt Fe, W, Mo, Co at 1380 ~ 1580℃ , pure metals in V, Nb and Cr, keep for 10~15min; then add intermediate alloys of W, Mo, Co, V, Nb, Cr and intermediate alloys of C-Fe, Si-Fe and Mn-Fe at 1280~1580ºC Alloy, keep it warm for 10~15min, stir evenly and remove the slag; add the bulk material pressed by Ti-C powder again at 1280~1580ºC, keep it warm for 15~35min; then add RE-M master alloy at 1280~1480ºC, keep it warm 3~5 minutes, the heat preservation process is continued with electromagnetic stirring; finally, it is cast in a vacuum furnace and the master alloy is obtained; S2: Electroslag remelting of the master alloy prepared in S1; S3: Drop-cast the master alloy remelted by S2 electroslag into a copper mold in a protective atmosphere to obtain a drop-cast ingot; S4: Crush the ingot of S3 and grind it into powder; S5: The S4 alloy powder is sequentially subjected to reduction annealing and powder compacting to prepare a powder block blank; S6: Sintering the powder block blank obtained in S5; S7: Perform graded heat treatment on the sintered powder block blank obtained in S6; S8: Forging and/or extruding, rolling, and drawing the powder block blank obtained in S7 to obtain a wire material of φ1-3mm; S9: The wire material obtained in S8 is subjected to graded heat treatment again. 2. The preparation method of powder metallurgy high-speed steel wire according to claim 1, characterized in that, in S4, the process of ball milling and powdering is as follows: S4-1: Crush the drop-cast ingot obtained in S3 to 0.1~1mm; S4-2: Use a planetary ball mill to mix the powder into alcohol. The weight ratio of balls to powder is 3~6:1, and the grinding time is 24~72 hours; S4-3: Dry the ground mixed slurry at 75~80°C for 5~10 hours, screen it and transfer it to a drying chamber with low oxygen partial pressure for certain pre-oxidation; S4-4: Seal and store the alloy powder obtained in S4-3. 3. The preparation method of powder metallurgy high-speed steel wire according to claim 1, characterized in that TiC, VN, WC, Mo ₂ C, Cr ₃ C ₂ , VC, and NbC are also added during the ball milling process. One or a combination of powders. 4. The preparation method of powder metallurgy high-speed steel wire according to claim 1, characterized in that, in the S7 and/or S9, the hierarchical heat treatment process is as follows: (1) Preheating: Heating to 580~620°C at a heating rate of 5~10°C/min, holding time t=3~5min/cm×d; (2) Secondary preheating: then heat to 840~860°C at a heating rate of 5~10°C/min, holding time t=2~4min/cm×d; (3) Quenching and heat preservation: then heat to 1170~1260°C at a temperature rise rate of 5~10°C/min, holding time t=2~4min/cm×d; (4) Quenching and cooling: Immediately afterwards, When d≥10, first cool down to 300~500℃ at a cooling rate of 10 ³ ~10 ⁵ ℃/s, with a holding time of t=0.1~1.5min/cm×d, and then cool down at a cooling rate of 10 ³ ~10 ⁵ ℃/s Cooling speed to 20~40℃, holding time t=0.1~1.5min/cm×d; When 10≥d≥5, cool down to 200~400℃ at a cooling rate of 10 ³ ~10 ⁵ ℃/s, hold the temperature for t=0.1~1.5min/cm×d, and then cool down to 200~400℃ at a cooling rate of 10 ³ ~10 ⁵ ℃/s. Cooling speed to 20~40℃, holding time t=0.1~1.5min/cm×d; When d≤5cm, cool down to 20~40℃ at a cooling rate of 10 ³ ~10 ⁵ ℃/s, and the holding time t=0.1~1.5min/cm×d; (5) Cryogenic treatment: then cool to -50~-150°C at a cooling rate of 10 ⁵ ~ 10 ⁷ ℃/s, holding time t = 1 ~ 2min/cm×d; (6) Tempering: then heat to 560~570°C at a heating rate of 5~10°C/min, holding time t=1~3h/cm×d; (7) Cooling: followed by rapid cooling to 200~300℃, holding time t=0.3~1h/cm×d, and air cooling to 20~40℃ after coming out of the furnace; (8) Repeat (6) and (7) 0 to 1 times; Among them, d is the maximum wall thickness of the sample, in cm. 5. The preparation method of powder metallurgy high-speed steel wire according to claim 1, characterized in that, in the S2, during the electroslag remelting process, the crystallizer outlet is used to strengthen cooling, side walls The temperature gradient of the molten pool is controlled by appropriate heat preservation methods, so that the acute angle between the solidification direction and the side wall of the molten pool ranges from 0 to 30°, and the purified master alloy melt is obtained. 6. The method for preparing powder metallurgy high-speed steel wire according to claim 1, characterized in that, in the S4, the D50 of the alloy powder prepared by ball milling is 8~50 μm. 7. The preparation method of powder metallurgy high-speed steel wire according to any one of claims 1 to 5, characterized in that, in the S5, the reduction annealing process is as follows: carried out in a vacuum furnace, in the furnace In a vacuum state or an inert gas protection state, lay the powder flat on the substrate with a thickness of 5~10mm. Multiple layers of substrates are placed on top of each other. The distance between adjacent substrates is 30~100mm. The temperature is 400~680℃. The holding time is 60~300min. After the furnace cools to room temperature, take it out. During the process, the oxygen content of the atmosphere in the furnace is detected to ensure that the oxygen content is less than 10 ppm. 8. The method for preparing powder metallurgy high-speed steel wire according to any one of claims 1 to 5, characterized in that in S6, the sintering method is normal pressure protective atmosphere sintering: (1) Pour protective inert gas into the sintering furnace and discharge oxygen so that the oxygen content in the sintering furnace is less than 1ppm; (2) Raise the temperature to 650~850℃ at a speed of 6~10℃/min, and the holding time is t=3~5min/ cm×d,; (3) Heating to 1180~1260°C at a rate of 8~10°C/min, holding time t=10~30min/cm×d; (4) Cooling to room temperature with the furnace; Among them, d is the maximum wall thickness of the sample, in cm.